Known stopper structures of a damper device used in a lock-up clutch for a torque converter are disclosed in, for example, Japanese Patent Laid-Open Publication No. Sho. 60-175865, Japanese Patent Laid-Open Publication No. Sho.61-252962, Japanese Patent Laid-Open Publication No. Sho. 62-56623 and Japanese Patent Laid-Open Publication No. Hei.3-194247.
With such known damper devices, it has been found that some stopper structures must be mechanically strengthened or reinforced by heat treatment due to the fact that the pressure-receiving area is narrow, and the remaining stopper structures are rather complex in construction. Thus, with the stopper structures used in these known damper devices, additional production steps are necessary when the damper device is manufactured.
Thus the aforementioned damper devices are not well suited to being manufactured in a way that allows the production costs of the damper device to be reduced.
A need thus exists for a damper device which can be produced at a lower cost, yet which is identical or superior to the known damper devices in construction and operational characteristics.